Manufacturing plastic bags

Abstract

In making a plastic bag having a filling pipe, to overcome the difficulty of separating the overlying walls of a flattened tube of plastics material, one wall (11b) of the flattened tube (10) is cut to form a flap (17) and the opposite wall (11a) of the flattened tube is cut to form an opening (14), registering with at least a part of the flap; two pairs of clamping members (22, FIG. 4) engage the flap at the location of the opening and are moved to cause the flap (17) to extend out of the plane of the first wall of the tubing; and the filling pipe (26) is then inserted between the pairs of clamping members (22) and on the inner side of the displaced flap to enter the space between the overlying walls of the tube. Thereafter the walls of the flattened tube are sealed around the filling pipe.

I claim: 
     
       1. A method of making a plastics bag having a filling pipe, comprising the steps of: cutting one wall of a flattened tube of plastics material to form a flap;   cutting the opposite wall of the flattened tube to form an opening, registering with at least a part of the flap;   inserting a pusher member through the opening to cause the flap to extend out of the plane of the first wall of the tubing;   inserting the filling pipe alongside the portion of the pusher member projecting through the first wall and on the inner side of the flap to enter the space between the overlying walls of the tube;   and thereafter sealing the flattened tube around the filling pipe.   
     
     
       2. A method according to claim 1, in which the opening end of the flap is constituted by a part of the open end of the flattened tube of plastics material and the opening in the said opposite wall is a recess extending from the same end of the flattened tube. 
     
     
       3. A method in accordance with claim 1, in which two spaced pusher members are inserted through the opening to cause the flap to extend out of the plane of the first wall of the tubing, and in which the filling pipe is inserted between the two pusher members. 
     
     
       4. A method in accordance with claim 3, in which each of the pusher members forms one of a pair of clamping members, the clamping members being moved together to draw the flap out of the plane of the first wall of the tubing. 
     
     
       5. A method in accordance with claim 3, further comprising holding the lateral portions of the flattened tube in a fixed position while the pusher members or clamping members operate to cause the flap to extend out of the plane of the first wall of the tubing. 
     
     
       6. A method of making a plastics bag having a filling pipe, comprising the steps of: cutting one wall of a flattened tube of plastics material to form a flap;   cutting the opposite wall of the flattened tube to form a second flap registering with at least a part of the first flap;   urging a pusher member against the second flap to cause both flaps to extend out of the plane of the first wall of the flattened tube, on the same side of the tube;   inserting the filling pipe alongside the portion of the pusher member projecting through the first wall and under the second flap to enter the space between the overlying walls of the flattened tube;   and thereafter sealing the flattened tube around the filling pipe.   
     
     
       7. A method in accordance with claim 6, in which the insertion of the filling pipe takes place while the flattened tube is still attached to a strip of plastics tubing sufficient to form a number of plastics bags. 
     
     
       8. A method according to claim 6, in which the second flap cut in the second of the overlying walls hinges in a sense opposite to the direction in which the first flap hinges in the first wall. 
     
     
       9. A method in accordance with claim 6, comprising cutting registering slots in the top and bottom walls where the neck of the bag is to be located to enable the tubing to be cut at the neck portion when the filling pipe has been inserted without the risk of cutting across the inserted pipe.